Mobile radiotelephone system having a single channel and a single frequency



Nov. 21, 1950 R. P. DIMMER MOBILE RADIO TELEPHONE SYSTEM HAVING A smcus CHANNEL AND A SINGLE FREQUENCY Filed Feb. 2, 1949 5 Sheets-Sheet 1 m 3 \r||I| NW w I c R mu S R mm m D S I Mww m I M A J V T 6 H w I E W T 7 5 US" l m w J EB. NM "L U 0 I G a m m 3 I Q R c I 3 2 I 3 4 I m I T W 3 m 8 M nc W R n W N g 0 9 I H wn u mi A an g 0. 0 w E c H n m n OUT LINE+ R mm N M M .l m N G I P. H T R E B 0 R V. B m 3 f 3 .II B E IIIIIIIIIIIIItEL Y m 2 a; L L N v A T A I L 2 N 0 dlL-l V ATTORNEY Nov. 21, 1950 R. P. DIMMER 2,530,315

MOBILE RADIO TELEPHONE SYSTEM HAVING A SINGLE CHANNEL AND A SINGLE FREQUENCY Filed Feb. 2, 1949 5 Sheets-Sheet 2 U V L E W /O 3 ww O T 5 50 5 I R R 0 M T S AU I 6 l6 D 0 0 l6 5: z S T T "L A n m RR RT M 05 M u nu ON 0 a 9 9 r. a A W E 2 D 4 5 0 RP I 2 2 L VMZL E L 0 RT |mw.\ M R N 5 0 w w o A H62 3 M 5 DO W E U 4 NM 0 om m 8 T c I l m R m 5 m w Hm m T\ '4. A6 6 8 h m HM D I A 4 R 2 2 a m u "fi m m 2 f 2 I l W k A 6 0 m 2 2 3 2 z z m m r L -I M m 45 m 8 w fi M/ 8 l ll, 2 5 6 5 4 LT? T 6 6 F 6 L 3 44 I. 1b! N m m ROBERT P. Dl MMER ATTORNEY R. P. DIMMER 2,530,815 MOBILE RADIO TELEPHONE SYSTEM HAVING A r SINGLE CHANNEL AND A SINGLE FREQUENCY 5 Sheets-Sheet 3 2; MW 3n my I x En n N l $23252 a 3. N N o \1 I23 :BJ 29E O to '0 ROBERT P DIMMER Nov. 21, 1950 Filed Feb. 2, 1949 x2855 uzo r on m 1 U r.. j 05 3m 0 P5QEQ 3528 2925 5502 m @I wmu a ATTORNEY Patented Nov. 21, 1950 UNITED STATES ICE MOBILE,RADIOTELEPHONE" SYSTEM HAV- ENG AwSINGLE CHANNEL-AND A'SINGLFL FREQUENCY.

Robert RBimrnen Chicago, Ill.', assign0r-to Auto's matic Electric: Laboratories, Inc,-, Chicago, 111,, iLCOI'POlfaLtiOn of Delaware Applicationiliebruary 2, 1949; Serial No. 74,134-

between mobile and exchange subscribers, and

vice versa, by meansof the fixed, or radio station equipment, withoutthe intervention of an operator.

A feature of ,the invention resides. in the provision of equipment at each mobile unit for releasing the radio station equipment which is under control of the mobilelsiibscriber, and in which a timedwrelease pulse is sent over the mobile units carrier responsive to the replacing of the handset on its switchhook. Thi incorn ing pulse is received at the radio stationand effectively initiates the release of the radio station equipment for handling other calls within short period of time after the mobile sub- ,scriber has brokenythe connection, thereby eliminatingneedless waste of time.

Another feature resides in the provision of a pulsereceiverat each mobile unit having alminor switch including a single level of bank contacts,

and which is operated responsive .to incoming;

pulses fOr identifying the call for a mobilewunit and to subsequently signal the mobile subscriber only when-a -call is intended *for him,

The invention, both as to its organization and method of operationtogetherwith further objects and advantages thereof, will bestbe understood byreference to the specification takencin connection with the accompanying drawingsin which:

Figure 1 shows a part of the -.centrali officerau-xiliary equipment' located in an automatic telephone exchange; :part vof the radio ,stationcontrol circuit, test "equipment and connecting lines 1 be- -tween, the central ofiice auxiliary; equipmentgand lithe radio; station rOOIltIOIiOiI'CHilJ.

1 mission l ofwradiol impulsesthebankcontacts of the minor switches in, the mobile stations are, wired according to. each ,mobilehstationstindividual callnumber, and that .,Fisure q2showsathememainderaof the radios-tation control circuit, the radio receiveruandhthe radio transmitte and the power control panel.

Figure 3-shows the radio receivery transmitter, andantenna and part ofthe mobile station'control circuit .of. amobile units Eigure 4 shows the-remainder 0f the mobile .stationycontrol,circuit, the pulse receiver, and

thedash unit.

.Figurefi showsamodificationof a minor switch which may ,besubstituted 9 for the minor switch 595 in .the pulse receiver, shown in Fig. 4.

The instant. disclosure shows .a single channel systemlproviding;complete secret service,.f ul1 selectiveiringing, dial tone, busy tone r-ing-back toneand answer signals in both directions.

The radio frequencyicarrier transmitted. from the transmitteraatrthe control. station and the radio frequency carrier transmitted from the transmittersat the mobile stationsare modulated by a 3000 cycle voltage bythe tone oscillators at the mobile and control stations for transmitting impulses, whilejthe tone. detectorstconnected to the receivers at these stations detect thesepulse modulations for translation. into switch controlt ling pulses.

"When a call i originated by an exchangelsub- ,scriber who .desires .to call. as mobile subscriber, a

special. first digit isldialed subsequent to the receipt of the :usual first-dial tone received from the first numerical; switch ,in the automatic switch itrain for connecting him with a radio levelin the selector of ltheiautomatic exchange. The :remaining two di its of the mobile subscriberfscall numberiare then dialed subsequent to the receipt of alsecond dial tonewhich indicates readiness to receive dial impulses forcontrolling the trans- It will be Inotedthat the calltnumber loisthe, mobile kstation shown (FigssB-and 4) is the twodig it number 47, while the; remaining contacts, withthe exception of the first contact (1:)land1the last contact (0) are connected lint-multiple.

A general callfeature islprovided in they-minor switch-4&5 in which ifiiteis desiredto signal-tall the .mobilesubscribcrs simultaneously, the operatorvatntheTcentralsomce exchange may dials the single digit which operates the minor switch at each mobile station for signalling the stations subscribers.

Having briefly described the apparatus involved in each figure and the various features and objects, a more detailed description of the equipment and its operation under diiierent conditions will follow.

Telephone office switching equipment Figures 1A and-1B of the copending application, Serial No. 55,627,-fi1ed October 20, 1948, of R. H. Herrick, shows automatic switching equipment in the telephone oflice which can be applied to the present application for completing this disclosure by connecting the four conductors I'll}, Ill, ll? and N3 of Fig. 1B to conductors I'll], Ill, Il2 and I73 in Fig. 1 (Central Ofiice Auxiliary Equipment) oi the present application. The descriptions and explanations in the specification of the above-mentioned copending application concerning the arrangement and operation of the automatic switching equipment shown in Figs. 1A and 1B can, consequently, be read as though such description and explanation were a part of the specification in the present application.

Telephone ofiice auxiliary equipment Figure 1 shows the Central Office Auxiliary Equipment connecting the Automatic Switching Equipment (Fig. 1A, 1B of the mentioned copending application) in the Central Ofice to the Radio Station Control Circuit 3863. This auxiliary equipment is usually located in the telephone exchange building but may be located at a remote point if circumstances so require. The automatic switching equipment is connected to the auxiliary equipment by talking conductors I ll and IE2, and by Out line simplex signalling conductor lie and In line simplex signalling conductor H5. The auxiliary equipment is connected to the radio station control circuit 3% by conductors lilil and lQl which constitute the Out line conductors, and by conductors I94 and I95 which constitute the In line talking conductors.

The auxiliary equipment comprises essentially a hybrid transformer I83 and an associated balancing network consisting of an adjustable resistor R3 and a capacitor C--I. The hybrid transformer Hi3 serves to effect the separation of incoming and outgoing voice currents as necessitated by the inherent one way characteristics of the radio transmitter and receiver. -The talking conductors I'll and H2 from the automatic switching equipment extend to the left-hand winding of repeating coil I85, with similar talking conductors from the right-hand winding of repeating coil 5B5 extending to the upper and center windings of transformer I83. It will be noted at this point, that voice currents from the automatic telephone office over conductors Ill and In are induced in the lower windings of transformer I83. Talking conductors are eX- tended from the outer terminals of the lower windings of the transformer I83 through normally closed contacts of key K-I to conductors I90 and I9I which constitute the Out line talking circuit to the radio station control circuit 300. The Out line simplex signalling conductor I'lll from the automatic switching equipment extends to the center tap of the lower winding of transformer I83. Conductors I94 and I95 comprising the In line talking circuit from the 4 radio station control circuit 30!! extend to the right-hand windings of repeating coil I8 1, and at this point, voice currents from the radio station over conductors I95 and H15 are induced into the left-hand windings of repeating coil I841. The talking conductors from the In line talking circuit are now extended from the outer terminals of the left-hand windings of repeating coil I8 3 to the center taps of the upper and center windings of transformer I83, through the left-hand upper and center windings to the right- ,hand winding of repeating coil I85, then from the left-hand winding to conductors ill and I72, to the automatic switching equipment. The In line simplex signalling conductor H3 extends to the inner terminals of the right-hand windings of repeating coil I84 through normally closed contacts of key K-I, contacts I32 and the two windings of relay I30. The Out line simplex signalling conductor extends to the center tap of the lower winding of transformer I83.

The auxiliary equipment also includes a timing arrangement for controlling the connection of simulated second dialing tone and simulated ring-back tones on calls outgoing from the telephone ofiice to a mobile unit. In addition to relay I31] this timing arrangement includes relays Ill] and I2!) and their associated temperature sensitive resistors R--l and R-2, which function in a manner to be described later in this specification. Continuous ringing voltage is supplied from the automatic switching equipment over conductor N33 for connection through contacts I3l of relay l3& and conductor I35 to the calling line. While interrupted ringing voltage is supplied over conductor lEM for connection through contacts I2I, H2, I3l and conductor N35 to the calling line.

Monitor jacks connected to the talking conductors of the auxiliary equipment provide means for monitoring calls between the telephone ofiice and the mobile units. Jack JI is bridged across the talking conductors extending from the righthand winding of repeating coil I85; jack J--2 is bridged across the In line talking conductors from the radio station; and jack J-3 is bridged across the Out line talking conductors to the radio station. All three jacks areconnected with suitable resistors in each conductor to maintain line balance and to prevent appreciable effect on an established conversation when the monitor equipment (not shown) is connected to any one of the monitor jacks.

A test key K-I comprising two sections is also incorporated in the auxiliary equipment. The right-hand section of the key KI provides facilities for determining whether or not there is a busy connection established between the telephone ofiice and one of the mobile units. The left-hand section of the key Kl provides means for turning the equipment of radio station control circuit 300 On or Off, as the case may be.

Radio station control equipment The right-hand portion of Fig. 1 and all of Fig.2 show the arrangement of the Radio Station control circuit 380. This equipment interconnects the automatic switching equipment (Figs. 1A and 1B of the aforementioned copending application) in the telephone exchange and the mobile units (such as illustrated in Figs. 3 and 4) by way of the auxiliary equipment (Fig. 1) in the telephone exchange and transmitter Zlll and receiver 200 (Fig. 2) at the radio station. The auxiliary equipment (Fig. 1) is "connected to the radio station controlcircuits "by conductors. l9iland |9| vwhich constitute :the Out line talking: conductors, ;.and .;by "conductors -l 94 and I95 which-"constitute the In line talking conductors.

.An Out line simplex signalling conductor ill] is. connected to thecenter tapof the lower winding of repeating coil 183, through theextreme left and right conductrs.fr0m"'the lower winding of coil 583, contactsof .key-K l, con

.tacts of jacks l92and I93, andthe two windings of relay I58 to the impulsing, or line, relay .250. Relay25c is operatedfrom the automatic switching equipment over Out line simplex .conductor no for causing the radio station transmitter 20! to be placed on the air, and for connecting the output circuit of tone oscillator 205 trolled by tone detector 2'35. Theoperation. of

the In line simplex signalling circuit will be explained in detail later. in this specification.

Radio station transmitter 29! cooperates with radio receivers 3538 of the mobile units bymeans of a radiofrequency carrier. Radio transmitters 3M of the mobile units EBB transmit a radio frequency carrier for operation with radio station receiver 200. to radio station receiver 290 from a mobile unit pass over In line circuit 290, attenuator 284,

band pass filter 203, and repeating coil [86 to In line talking conductors I94 and I95 leading to the telephone office auxiliary equipment. The attenuator 2% permits adjustment of the radio station receiver output to the relatively high level required (approximately 50 milliwatts') for positive operation of tone detector 205, and

also to deliver. the normal level of approximately a .20 milliwatts maximum tothe In line circuit.

Band pass filter 263 provides means for rejecting noise and other frequencies below .300 and above 2600 cycle to improve the overallsignalto-voice ratio of thecircuit.

Monitor jacks connected 'to.the talking conductors of the radio station control circuit pro- ;vide means for monitoring calls between the telephone. office and the mobile units. Jack J-B is bridged across the In line talking conducr tors from the radio, station receiver 200; jack J'4 is bridged across the In across line talking conductors from the auxiliary equipment just ahead of the simplex transformer I83. Jack J-5 is bridged across the Out line talking con- ,ductor from the auxiliary equipment just ahead of simplex transformer I83; and jack J-1 is bridged across the Out line talking conductors to the radio station transmitter 20! beyond simplex transformer l83'for monitoring the radio station transmitter modulation input. All four jacks are connected with suitable resistors .in each. conductor to maintain line balance and to ,preventappreciable efiecton an establishedconversation when. the monitor equipment (not .shown) is connected .toany one of the monitor Pjacks.

The radio station control circuit 30!) also in- Qcludes cut-01f jacks for splitting the In line circuit and the Out line circuit .fortesting or The audio frequencies incoming W "6 like aapnrposea The insertion" of. 1a plug (not shown) into jack I96 splitsithesfiln"lineacircuit towards the. auxiliary, equipment, while the insertion of a plug (not shown) into'jack I91 splits the. In. circuit towards the radiozsystem. The insertion of a plug (not shown) into jack 193 splits the Out line circuit towards theaux- .iliary equipment, and the insertionofa plug (not shown) into jack |92msplits theffOut linecircuititowardspthe radio system.

Supervisory lamp signals are. incorporated 'the radioistation control .circuit 300 for enabling maintenance personnel at the radio stat-ion to note the operating condition of the'circuit. One

lamp L--1 functions toindicatethat radio station transmitter 28! .has been started. Another lamp. .-L5 functions -to indicate when the radio station transmitter carrier is onthe air, as: contrastedwith lamp L.'l indicating that trans- .mitter 20!. has only been started. Theglowing of .both lamps simultaneously indicates that transmitter 20 I is functioning; properly.

Transformer 284 is the only power transformer in the radio station control. circuit 3llllcontin- ,uouslyactive, even though the rest of the equipment in control circuit sen isv turned Off. Transformer 284 can be made inactive only by the operation of master switch 269., which operation disconnects the main alternating current power supply (for example, 115 volts, cycle) to control circuit 363 and thereby render the entireradio station equipment dead. Transcontrol of all radio station equipment, including transformer 284, in the hands of maintenance personnel primarily for personal safety. By this control, a maintenance man makes the entire radio equipment dead in order to protect himself while working on portions of the equipment which would endanger him if it were unexpectedly energized. Supervisory lamp signal L8 glows whenever master switch 289 is in the operated position.

Control circuit 380 further includes a source .of 48 volt direct current and of 250 volt direct cur-- .rent. The 4.8 volts direct currentsupply may be derived from a volt alternating current supply through a conventional dry-disc rectifier 206 with an inductive input type of smoothing filter. The 48 volt direct current thus made available is utilized for operating the relays at theradiostation and certain of the supervisory lamp signals. The .250 volt direct current supply is derived through a conventional tube rectifier 281 using a type 5Y3GT/G vacuum tube with small capac- .ity input type of filter from the 115 volt alternating current supply. The v250 voltdirect current thus made available is used-tor the anodes of tone detector and. tone oscillator 205. A winding of transformer 283 supplies the heater of tube- 205, one section of'which acts" as a tone detector and the other section which acts as a tone oscillator.

Separate fuses (not shown") are alsolprovided "for the various power supplies of the radio station control circuit 300.

Mobile station control equipment Figures 3 and 4 show the arrangement of the .mobile station control equipment.

All of this equipment is located in the mobile unit and is suitably mounted therein. The mobile station control equipment may be sub-divided into the dash unit 40L the mobile station control circuit:

known radio receiver 300 and a well-known radio transmitter 30!. It will be noted that both the receiver 300 and transmitter 30i use the same antenna (not shown) for receiving and sending the carrier frequencies. The talk-listen relay 335 in the transmitter 30! is provided for switching the antenna from the receiver to thetransmitter and then from the transmitter to the receiver responsive to the depression and restoration of a talk-listen button M5 in the handset 303. A dynamotor 315 in the transmitter is operated by the relay 32E whenever the handset 303 is removed from the switchhook 402 for providing power for the transmitter 30I and for the handset 003.

The dash unit MI is comprised mainly of handset 403, switchhook springs 302, dial 400, buzzer dill, master switch :08 and indicator lamps L-B and L-0. Handset 003 contains a talk-listen button 055 which is depressed during talking and released during listening.

The mobile station control circuit 300 is comprised mainly of vacuum tubes 305 and 300, minor switch 005, attenuator 30d, and the necessary relays, transformers, conductors, resistors and condensers. Tube 305 has two separate and distinct functions: one is to operate as a detector for rectifying incoming pulses from a calling line for operating minor switch 5-05, and the other is to operate as an oscillator for providing 3,000

cycle voltage which is later controlled responsive to dialing and sent to the transmitter Sill as splashes of tone pulses. Minor switch 405 is shown as a rotary switch having a single level of bank contacts, with the bank contacts being wired according to each mobile units individual call number (which in Fig. 4 is shown to be the number ii). Attenuator 300 is provided for permitting adjustment of the radio station receiver 300 power output to a relatively high level (approximately /2 watt) for operation of tube 305, and "also to deliver a normal level of power for the handset 003 (approximately 6 milli-watts).

When an incoming call (via the fixed radio station equipment) is initiated, the carrier received "rom the radio station transmitter 253i causes squelch relay Bid to operate and prepare the mobile equipment ior receiving the call. Tube which acts as a tone detector, is operated on in coming pulses of tone from the fixed station and rectifies these pulses for operating relay H0. Relay iiil causes the stepping operation of minor switch 005. The first digit of the car's call number is dialed and relay H0 pulses correspondingly for causing motor-magnet 430 to step wiper 505 of the minor switch 400 to a contact corresponding to the first digit dialed. The'minor switch 405 then restores between digits and after restoration, when the second digit is dialed, motor-magnet 030 again positions wiper 406 accordingly, at

The radio units comprise mainly of a wellwhich time relay 410 is operated to signal the called mobile subscriber of an incoming call.

When an outgoing call (from the mobile unit) is initiated, the transmitter 301 is connected with the antenna and the car's carrier is put on the air for approximately two seconds for starting the fixed stations equipment to seize a line in the central office. The time delay equipment including tube 306 operates which disconnects the transmitter I from the antenna and connects receiver 300 to the antenna. Dial tone from the automatic exchange modulates the carrier from the fixed station which is then received and sent to the handset via receiver 300. Tube 305 was changed to operate as an oscillator in response to the removal of the handset, and in response to the operation of the dial transmits a 3,000 cycle dial controlled voltage to the transmitter which sends these pulses to the fixed station. The automatic equipment at the central oflice operates in the usual manner and the call is completed as a regular telephone call.

Outgoing call (exchange subscriber oz'a fixed station to mobile subscriber) The operation of the fixed, or radio station equipment during an outgoing call from an exchange subscriber to a mobile subscriber will now be explained, reference being had to Figs. 1 and 2.

It will be assumed that the subscriber at station T (Fig. 1A of the aforementioned copending application) has originated the call by removing his receiver, and that the equipment at the automatic exchange (Figs. 1A and 1B of the aforementioned application) has operated and transmitted a first dial tone back to subscriber T in the usual manner.

It will also be assumed that the radio station equipment has been energized and has been made ready for handling both incoming and outgoing calls in the following manner. The operator at the radio station closes local master switch 209 which supplies 115 volt cycle power to transformer 284. The wire chief at the central oflice auxiliary equipment station (Fig. 1) momentarily operates key KI, thereby energizing relay 450 over a circuit from battery at I02, through operated contacts at key K-I, over the Out line conductor I90, through (normally) closed contacts of test jacks I93 and I92, the lower lef hand winding of repeating coil 18?, the lower winding of relay I50, the upper winding of relay I50, the upper left-hand winding of repeating coil I81, the normally closed contacts of test jacks I 92 and I93, the Out line conductor I and the operated contacts of key KI' to ground at The flow of current through both windings of relay I50 is in an aiding direction to operated relay I50. In operating, relay I50 opens the energizing circuit of relay 250 at contacts I53, and at contacts I54 completes a circuit for operating magnet 2'20 of the ratchet switch 202. This circuit may be traced from ground at contacts I54, conductor I59, winding of; magnet 21!! to negative battery at rectifier 206. Key K-I is returned to normal and relay I50 is deenergized. At contacts I54, relay I50 opens the circuit to magnet 210. It will be noted that when magnet 210 was energized it attracted its armature and held it in that position; As magnet 270 restores, the spring action against the armature causes the ratchet switch 202 to step one step. Ratchet switch 202, thus closes the contacts in the microswitch 208 which now completes the energizing circuit for the ratio station control equipment 300i Thereby, *power is supplied to the transformer 283, the radio receiver 29c, radio transmitter ZElI, filaments of tube 205, relays and indicating lamps. At contacts 21!, ratchet switch 202 supplies 48 volt battery supply from rectifier 255 to all the relays.

When the-exchange subscriber T receives the first dial tcne'as-an indication for dialing, he then dials a certain specified-first digit of the desired call number. Responsive to the certain first digit being dialed-the automatic exchange equipment operates in the usual manner and a "radio level of the central ofiice selector switch is reached, at which time a groundpotential is subsequently placed on the Out simplex line conductor Ill].

The ground on the Out simplex conductor H completes a circuit for energizing relay 255} through both windings of differential relay 45% in parallel. This circuit may be traced follows? from grounded --sir1plex Out conductor M0 to the center of the lower winding of transformer I83 where the circuit then extends over two branches in parallel including the left and right-hand lower windings of transformer I83, normally closed contacts of key K--I, conductors lililand lei, normally closed contacts of the test jacks- I83 and 582', upper and lower lefthand winding of repeating coil idl, through the upper and lower windings of differential relay I50, where these parallel circuitsjoinand extend by way of contacts I53 and the winding of relay 250 tobattery. The current flow through Windings of differential relay I50; at this time, are in opposing directions with the result the two windings oppose each other and the relay does not operate its armature. Relay 2%, however, is operated over this simplexcircuit.

In operating, relay 250 completes an obvious circuit to relay 250 at contacts-253, and at "contacts 252 completes a point-inthe outgoingline 28b to the transmitter 25%. Relay use (which is slow-to release) remains operated during dialing. At contacts 2t2 and-264, relay ace completes the plate circuit for tube '205to" operate as a tone oscillator. At contacts 255, relay 2% supplies a starting ground potential for placing transmitter 25% on the air. Responsive to the radio trans mitter being started, a circuit is completed for operating relay Mil by placing ground on conductor 2&0 in the transmitter. This circuit may be traced from ground in transmitter 205 over conductor 24%, contacts 2H, conductor IE3 and;

through 'thewinding of relay Mllto battery.

In operrelav on a-circu-it for relay we at contacts Ml. and M3: The circuit for energizing relay 5353 may be traced from ground at contacts 543, the upper left-hand-wind-- ingof repeatingcoil 5'85, the normally closed contacts of'testjacks l9? and 05; conductor ES 4 ofthe ln lin uppenriight-hand winding of repeating coil I8 3, theupper winding of relay 39; the lower winding of relay {3%, thelower right hand, winding of repeating ccil' I84, conductor le'sertae m" line, normally closed con tactsof test jacks lfifiand 981, the lower lefthand windingpf repeating coil lee andto bat tery through contacts Ed I; of relay ItdIbeing connected in series, aid each other with the result that relay iiiil operates in response to the operation or relayide.

'In operating contacts I31, relay i30 completes a second dial tone circuit back tothe calling lineover conductor lll5jfrom the tone source con,- nected to'conductor I031 At contacts I32, relay The two windings acsogsiei lin'g'circuit, and at'oontacts I33 completes a 'cir-a cuit for the relays I I0 and I20. The circuitifor relay I I01 maybe traced from ground at contacts and; through the winding of relay I II) to battery. The. circuit forrelay lmay be traced from ground;

I33, temperature sensitive resistor R| at contacts I33, down through temperature sensitive resistorR-Z and through the winding of relay I20 to battery. Approximately five seconds after the circuit to relay H0 is completed, the

resistance of RI has decreased sufficiently to allow enough current to flow for relay M0 to, operate. At contacts II I, relay H0 removes second dial tone from the calling line, at contacts;

tacts I22, relayl20 completes a locking circuit for itself.

Upon receipt of the second dial tone, the exchange subscriber dialsthe remaining digits of" the call number. Pulses corresponding to thenext digit dialed are transmitted to the pulserelay 250 which restores a number of times corresponding to the number of pulses transmitted. Upon each release of relay 250 at contacts I, dial pulses are converted to corresponding splashes of tone of about 3,000 cycles and are sent to the radio transmitter 20I over the outgoing" line 280. Since the tone oscillator part of tube 205 is now operating, the anode-cathode circuit output of the tube is applied to the primary winding of transformer 285. The secondary winding of transformer 285 sends the tone oscillations to the outgoing line 280 by Way of contacts 2!? and are converted to splashes of tone at contacts 251' by relay 250.

The tone splashes corresponding to dial pulses are sent over the outgoing line 280 by the pulsing.

relay250 to modulate the radio stations carrier and these modulations are received at the mobile unit in a manner to be explained later. Responsive to dialingthe last digit of the call number, corresponding pulses of tone again modulate the carrier and are transmitted to the mobile unit.

in .a similar manner.

Upon completion of dialing, the mobile equipment operates to signal the mobile subscriber of an incoming call. Upon answering by the mobile subscriber, a carrier from the mobile unit. is received atradio receiver 200. When the carrieris received at radio receiver 202i, a ground is applied. to conductor 229 for operating squelch,

relay 210 overan obvious circuit.

Upon operating, circuit to relay I40 at contacts 2; at contacts 2I2pr'eparesalocking circuit for relay 230; at contacts 2I3:comp1etes a circuit for relay 220 which may be traced from ground at contacts 242, contacts 2I3, up to contacts 23! and through thewinding ofrelay 220 to battery. At contacts 2 I 6 squelch relay 2 I0 prepares a point in the talking conductors of the outgoing line 280, at contacts 2 H the output of the tone oscilllator isremoved from the line, and at contacts 2I8 maintains transmitter 20I energized during conversation. In operating contacts 22I, relay 220 completes an obvious locking circuit for squelch resquelch relay 2l0 opens the lay 2I0. When relay I40 restores, the energizing,

circuit for relay I30 is opened at contacts MI and I43. Relay I30 restores and at contacts I33 opens the locking circuit to relays H and I20 which then restore. The tone transmitted from conductor I04 and back to the calling station over conductor I05 is now disconnected.

Conversation may now proceed in the usual manner and upon completion of the conversation and in response to the exchange subscriber hanging up, the circuit is opened to relay 250. As relay 250 restores contacts 253, the circuit to relay 260 is opened. After the mobile subscriber replaces his handset, modulated carrier from the mobile transmitter is automatically placed on the air for a two second duration in order to release the connection.

It will be noted that since squelch relay 2 I0 is still operated, and relay 260 has restored (which then completes the plate circuit at contacts 263 for the tube 205 to operate as a tone detector), the steady two second incoming release pulse of modulated carrier from the mobile unit is rectified by the tone detector of tube 205 and a circuit iscompleted for operating relay 240 for a two second time interval. This circuit may be traced from the left-hand anode of the tube 205, through the winding of relay 240, contacts 26I and through resistance R-I0 to the left-hand cathodeof tube 205. 0

Before continuing with the present operation, it will again be noted that -at the time the mobile stations carrier came on the air, relay 2I0 operated-and at contacts2l3: completed an obvious circuit for relay 220, which upon operating provided an obvious locking circuit for relay 2H] at contact 22 I. When the two second release pulse was modulated with the mobile stations carrier, the detector part of tube 205 passes current and relay 24!: operates as described above. At contacts 24!, relay Edi) completes a circuit for slow-tooperate relay 230 and at contacts 242 opens the circuit to slow-to-release relay 220. Relay 230 will, however, operate just ahead of the restoration of relay 220 and will lock up over an obvious circuit at contacts 232, and at contacts 23I opens a further point in the circuit to relay 226. Relay 220 now restores and opens the locking circuit of squelch relay 2I0. At the end of the two second interval (the time of the release pulse), both the carrier and release pulse of the mobile station are removed from the air. The energizing circuits for relays 2 I0 and 240 are therefore opened, and relay 240 will restore just slightly ahead of relay 2I0. In restoring, relay 240 opens the energizing circuit to relay 230, which however remains operated over its locking circuit. Relay 2I0 now restores and at contacts 2I2 opens the locking circuit to relay 2%, at contacts 2I3 opens the In line simplex signalling circuit to release the automatic switch train, and at contacts 2"! removes the starting potential for radio transmitter 20I, which then removes the radio stations carrier from the air. Relay 230 now restores and the radio station is at rest and conditioned for future calls.

Incoming call (mobile subscriber via fixed station to exchange subscriber) The operation of the fixed, or radio station, equipment during an incoming call from a mobile subscriber to an exchange subscriber (or another mobile subscriber) will now be explained, reference being had with Figs. 1 and 2.

It will be assumed that the radio station equipment has been made ready to receive and make calls in the same manner as described under the section entitled Outgoing Call and that the mobile subscribers equipment shown in Figs. 3 and 4 is that of the calling party.

As the mobile subscriber at the mobile unit removes his handset, his radio transmitter is placed on the air for approximately two seconds. It will be noted that as neither relays 250 and 203 are operated, the plate circuit is prepared to the tone detector part of tube 205.

The incoming carrier from the mobile transmitter causes ground potential to be applied to conductor 229, which will operate squelch relay 2I0. In operating contacts 2 I2, squelch relay 2I0 prepares a circuit for relay 230. At contacts 2 I3 squelch relay 2 I 9 completes the In line simplex signalling circuit, and also completes a circuit to relay 220, which may be traced from ground at contacts 242, contacts 2I3, 23I, and through the winding of relay 220 to battery. At contacts 2I4, squelch relay 250 completes the plate circuit for the tube 235. At contacts 2II the output of the tone oscillator part of tube 235 is opened. At contacts 2H3, squelch relay 2I0 applies a ground potential by way of conductor 233 for starting radio transmitter 20L Upon operating, relay 223 completes an obvious locking circuit for the squelch relay 215 at contacts 22 I.

The starting of radio transmitter 20I (responsive to the closing of contacts 2I8) causes the radio stations carrier to be placed on the air.

The signal In simplex conductor H3 is grounded at contacts 2I3 by the operation of squelch relay 2 I 0 to cause the operation of a relay in the automatic exchange equipment (similar to relay 110 shown in Fig. 1B of the copending Herrick application, Serial No. 55,627, filed October 20, 1948). The circuit for grounding conductor I'I3 may be traced as follows: grounded contacts 242, contacts 2I3 to contacts I5I and thence over two parallel paths including contacts I42 and I44, both left-hand windings of repeating coil I86,

both In line conductors, normally closed contacts on test jacks I91 and I36, conductors I94 and I95, both right-hand windings of repeating coil I84, and through opposing windings on difierential relay I33 when the parallel paths again join and extended by way of contacts I32, upper normally contact of key KI, to the In simplex conductor [13 and to the aforementioned 'relay in the automatic exchange to battery. The

relay in the automatic exchange operates, as explained in the copending application to cause seizure of a numerical switch in the automatic exchange. The seizure of this numerical switch causes dial tone to be transmitted back to conductors Ill and I12. This dial tone is transmitted through the coils I and I83, over the Out line to coil I8! and thence to the radio transmitter over line 280 and superimposed on the carrier for transmission to the mobile station receivers. This carrier operates the mobile stations radio receiver, and responsive to dial tone being transmitted to the radio transmitter from the regular automatic exchange via the Out line, the mobile subscriber is informed that dialing may be started.

The modulated carrier dial pulses from the mobile subscribers radio transmitter 30I are received by radio receiver 205 and sent over the In line 290 and applied through transformer 286 to the grid of the detector part of tube 205 and are rectified therein. The rectified pulses operanswers atez'relay .24fl,r.oncee for each rpulse, overfia circuit fronritheiplate of the'detector, relay. 249, contacts '2 6:1 and resistance: R -i to the filament I of the detector-part of tube 205.

In operating, relaytZ lB completes. an obvious circuit for relay 230' at contacts 24!. At contacts 242,2relay 24s transmits thesepulses over the In line signalling circuit'to the. automatic exchange.

The pulses received at the automatic exchange operate a relay which repeats loop pulses to operate the automatic switches to extend the callv'to thecalled automatic subscriber in the wellknown' manner. Upon completion 0t dialingythe mobile subscriber receives a ring-back tone, when the called party is being rung, from the regular exchange lin th'e usual =way; viathe Out line conductors I 9E) and ill! through the repeating coil 1i lii'i, the Out li ne ZSB to radio-trans mittemlZEll, and hence to the mobile-station.

"Relay-23i'is a slow-to-operate relay and will not operate during dialing because the ground pulses at contacts 24 are or too s'hort'a duration. "'Relay 23fl is only operated on the' long release pulse.

250" is operated froma ground potential placed on' 'the Out signalling conductor l'lilfromthe automatic' exchange over .a circuit previously traced;

I-n operating'contaots 252, relay 'wllcompletes' a point the circuit of the Out line 280; At contacts 253, relay i'ecomp'letes an obvious circuit/" ierrelay 26G; At'contacts 26 i, relayfltll opens the platecircuit'of the detector 'partof the tube'ZfiEi an'd at contacts 265; relay 260 maintains the radio transmitter Z-fll energized.

Conversation now proceedsinthe usualmanher; and upon completion, thehanging upof the exchange 'subscriber opens the circuit to release relay 258,wh-ich in turn releases relay 260. In restoring contacts 263; relay 253 again completes a point in' the plate circuit of the tonedetector part of tube ZDB, and at contacts itfi removes one of the starting grounds for radio transmitter L When the mobile subscriber replaces his handset, a release pulse of 'modulate'd carrier'from the mobiletransmitter' is placed on the air for approximately two seconds; and since squelch relay-2i a is operatedand relay 250*- has restored, thetone detector part of tube 2H5 is againoperahle. m whichcase, upon receipt of the two second continuous release pulse from the mobile transmitter, tube-2-il5 rectifies this pulse and-passes a steady current"for operating-relay 240 over i a previously traced circuit.

In operatingcontacts 241, relay 240 completes an energizing circuit for a time duration'sufii cient'tmoperate relay 23! opens the circuitior 'relay 220.

Therestorin'g of slow-to-release'relay 2.20. opens matic switch train, and at contacts 218 removes the starting potential forfradio.transmitter 201,

whichthen removes the radiostations carrier from the air.

The radio station control-equipment is now. at restland. conditioned for future.:ca1ls..

When the calledautomatic sub scriber answers by removinghis receiver; relay In operating, relay 230 locksup'at contacts 232"and"at'contacts23l 1 radio transmitter 30L through resistor R6 to the cathode.

f4; Outgoing i'call from mobile subscriber The operation of the mobile equipment dur= ing the origination and completion of an outgoing call from one ofthe mobile units will now be explained, reference being had with Figs. .3 and 4 ofthe drawings.

It willbe assumed that the mobile unit'subscriber has energized his equipment by closing the master switch ens which supplies power for the equipment from battery 489. It will be noted that the positive terminalof battery .409 is connected to the frame of the car and that all the ground symbols shown are likewise connected to the frame of the car.

In. order to initiate an outgoing call, the mobile subscriber removes his hand-set 693 from the switch hook. As soon as hand-set 403 is removed from the switch hook a circuit is completed for relay 3:30, with this circuit being traced from the grounded contact at switch hook springs 402", conductor 397, contacts 5H5, up from conductor 395 and through the winding of relay 366 to battery. Inoperating contacts 3%, relay 368 completes'an obvious circuit for the relay 3215 in the At contacts 3613, relay 350 completes a point in the talking circuit from radio receiver Silt to the hand-set 483. At con tacts 365, a point in the charging circuit for the condenser C2- is prepared. At this time it will be noted that when the master switch 408 was closed, a circuit (not shown) was completed toa vibrator (notcshown) of the well-known type, in the radio receiver. 395, which supplies the high positive (+180 v.).potential to the plate circuits of tubes 395 and 39%? and for chargingcondensers C2, C3 andC4. The plate circuit for tube 305and condenser C2, however, is at present still open at contacts The plate circuit for tub e'396 is completed,..as soon as-the high potential is supplied, over a circuit including conductor 349 throughthe-winding of relay 3262 to the plate of tube 395.. The potential to the cathode of tube 305 may be traced from conductor 349 and Tube 3% now passescurrent and energizes relay .320, which prepares a point in the energizing circuit to relay 638. The charging circuit for condensers C3 and Gamay be traced fromthe-positive v. source. in radio receiver 3m], conductor 349, up through resistor R8, up and to the right andto' the upper andleft-hand plates of condensers C3- and C4 respectively, Groundpotential is supplied to thelower and right-hand; plates of con.-

densersC3 and Cd by Way of contacts 345 and 3fifi respectively. To continue with the presentv operation of relay 3E9at contacts 36! the dischargecircuitrof condenser or. in the timing cir-" cuit of the time delay tube 365 is completed.

,This discharge circuit may be traced from'the circuit. for relay-335 may be traced from. ground atcontacts 368, contacts 3E2, 32i and through the winding of relay 330 to battery, but since relay twins-constructed as being slow to operate;

i the relay will not operate during the present "IBI cycle of operations as: its energizing circuit will be-subsequently opened. The'circuitforrelay35D mays beatracedifromground'at contacts 3623, contactsf3l2land. 3H upland tothe right and downthroughrthewinding of relay 350 to battery; The; circuit ffortrelay 335"may be traced fiom groundat contacts 368, contacts 3I2 and3l I, up and to the left through resistance R1 and through the winding of relay 335 to battery. At contacts 369, relay 3H completes its own looking circuit to switch-hook springs 492, at contacts 311}, a point is opened in an alternate path of the high potential charging circuit for condenser C2 and the plate and grid supply to tube 335, and at contacts 3'! l, the audible signalling circuit to the mobile subscriber is opened. The closing of contacts 363, which completes the incoming talking circuit to the handset 403, also makes it possible for the mobile subscriber to receive dial tone.

In operating contacts 325, relay 325 starts the operation of dynamotor 375, which provides power for the radio transmitter 3i and handset 463. In operating contacts 352, relay 35% changes the plate circuit of tube 395 to operate as a tone oscillator, at contacts 35% a point in the oscillator output of tube 385 is prepared for subsequent impulse transmission, at contacts 355 the cathode "of tube 363 is grounded to prepare a further point in the plate circuit of tube 335 and at contacts 356 the plate supply of tube 3&5 and the charging circuit for condenser C2 is completed. The last mentioned circuits may be traced from the high positive potential in radio receiver 366, conductor 339, contacts 356, conductor 395, contacts 155, and divided, (1) by way of conductor 394, resistor R5 and contacts 365 to the left-hand plate of condenser 02, (2) by way of conductor 389, lower left-hand winding of transformer 383, contacts 352 and to the plate of tube 305. The right-hand plate of condenser C2 is connected to ground. In operating contacts 336 and 33?, relay 3-35 disconnects the antenna from radio receiver 353 and connects the antenna with radio transmitter 3Bl, which thereby places the transmitter on the air.

In summation, it will be noted that as relay 36d operated, the above described results for all practical purposes occurred almost simultaneously, in which a discharge circuit from condenserCt was completed for stopping tube 365 from passing current to thereby release relay 326; relay 325 was operated for energizing radio transmitter 31H; relay 335 was operated to disconnect the antenna from the radio receiver 3&3 and to connect the antenna with the transmitter 3G! for placing the transmitter on the air; and relay 359 was operated to change tube 305 for operation as a tone oscillator during impulsing, with relay 351! also completing the high potential voltage supply for tube 395 and for charging condenser C2. To further describe the operation of condenser C4, it will be seen that as the discharge circuit of condenser G4 was completed, the discharge of condenser C4 caused a change in the grid bias of tube 306 which then ceased passing current and which in turn caused relay 323 to restore. Resistance R4 has been given a value which limits the discharge time of condenser C4 to' approximately that as soon as relays 325 and 335 have oper-' ated, the mobile stations carrier is placed on the air. The mobile stations carrier remains on-the air until after condenser 04 has dis-- 16. charged and tube 336 has again started passing: current, at which time relay 320 is reoperated" and again completes the circuit for relay 330 at contacts 32!. After the expiration of its slowto-operate time, relay 335 operates contacts 332 and applies battery potential directly to both sides of relay 335, which serves as a shunt and causes relay 335 to restore. The restoring of relay 335 removes transmitter Bill from the air. by disconnecting the antenna from transmitter 38! and reconnecting the antenna with radio receiver 308. I Assuming for the instant that the radio station is busy or in use, an outgoing carrier transmitted from the radio station would be received at each mobile stations radio receiver such as 30D and cause the operation of each mobile sta tions squelch relay such as 3H]. In operating contacts such as 3! I through 316, the operation of each relay such as am would prevent the operation of each relay such as 363 which in turn would prevent a future calling mobile stationscarrier from being placed on the air. Also as: an added busy indication, if a call had been ex- ;tended via the radio station to one of the movile 1 stations, all the minor switches such as 405 in all the pulse receivers of all other mobile stations would be operated and the relays such as 450. would be operated responsive to a diflerent first or second digit for closing a circuit to light allbusy lamps such as L8. It is thought that this paragraph will sufiice for the present description,: since a more detailed explanation will follow in the section entitled Incoming Call To Mo bile Subscriber. However, since it has been previously described that the calling mobile Sta-1 tions carrier has been placed on the air, the radio station is therefore not busy.

During the time that the mobile stations car -1 rier was on the air (approximately two seconds) the outgoing carrier was received at the radio control station and operated equipment therein such as described in the section entitled Incoming Call (Mobile Subscriber Via Fixed Station to Exchange Subscriber) for causing a trunk line to be seized at the central office. Responsive to said seizure, an acknowledged carrier is placed on the air by the radio control station for op erating all the squelch relays such as 3 H3 in all the mobile stations (with the exception of the calling mobile station at the present) for the purpose of locking out all the mobile stations but the calling I one.

When relay 335 has restored responsive to the expiration of the discharge time for condenser C4, the antenna is returned to radio receiver 300 as previously stated. The radio stations carrier is received at the calling mobile station and causes a ground potential to be placed on conductor 348 for completing an obvious circuit to the squelch relay 310. In operating contacts 3 and 3I2, relay 3!!! opens the circuits to relays 339 and 350. At contacts 3 l 3, relay 3!!! completes an obvious locking circuit for itself, at contacts. 3l5 a point in the original energizing circuit of relay 369 is opened, and at contacts 3l6 a point in the circuit for supplying an operating ground to the minor switch 435 is prepared, in addition, a point in the circuit of buzzer All? is also prepared.

In restoring, relay 33d removes the battery shunt from relay 335 at contacts 332. Relay 350, will now restore, having no efiect on the equipment at the present other than to conserve the potential of battery 409, since each subsequent transmitter 33!. '-'traced from thesecondary winding of trans- .formerr383, contacts 35 i, resistorR-S, conducdepression of ,talkr-listen button "415 and each :rota-tionof dial 404 willcomplete areenergizing {circuit for relayx350.

The incoming carrier from the radio station causes the radio receiver 30!] to transmit an audio frequency to thehandset 403, and which serves as a dial tone indication to the mobile sub- "scriber that he may-now dial the desired call number. As soon as-the dial is rotated for the first digit, the dial off-normal springs ON are.

closed, again completing a circuit for the relay 353, which :may. be traced from ground at the switch hookusprings 432, through the dial offnormal springs ON, conductor 393 and through the winding of-relay 35!) to battery. It will be noted that the operation of relay-353 again completesthe-previously described circuits for the itube to operate as a. tone oscillator.

dialr ltfi is allowed to restore, intermittent ground pulses, caused by.-theinterrupter springs of the As the dial,. operates i the relay iEit oncefor each pulse.

At the pulsing contacts 422; relay 42! applies dial pulsesin theforrnof tone splashes (3,000 cycle voltage from the tone oscillator 395) to the radio These 3 tone splashes may be :tor 33?, contacts 422, conductor 335 and to the input wind-ingot the transformer in the radio transmitter 3t 5 where these tone splashes modulate the carrier. It will be also:noted. that as the Thiscircuit may be traced from restore after each digit is dialed. Relay 335,

-.therefore, operates atthe same time asrelay-350 land .again con-nects thetransmitter' 33 i with the antenna for placing the mobile stations carrier,

.modulated with. the tone splashes corresponding to diallpulses -ontthe air. -After the dial 404 .has returnedito-normal: at the end ofthex'iirst digit dialed, relays35i! and 335 arereleased responsive to .theopening-of the dial off-normal springs ON.

Thedialing ot a second digit of the called-number, operates the equipmentwin the same manner .as-sdescribed during thesdialing of the-first digit, =with relays 35d and Z335-operating' assoon-as dial LEM isrotated off-normal, Land 'relays iflii'operating responsive t-to: each pulse of. the: dial. Uponpcom- :pletionrof dialing, vrelays i35fih2tlld .335. again restore, with :the antenna returned to the receiver .itfiii.

The radio control'station equipment receives zthe. mobile stations carrier; which ismodulated -with the aforementioned splashe 1 of =tne, and detects these splashes and -sends-"corresponding switch-controlling pulses to the automatic exchange, wherein they" are transmitted over a seized linkto operate; automatic switches to con meet with the called party. The ringing ,ofithe calledparty is completedfinthe usuaLmanner.

may. now. proceed. inthe usual manner, with the mobile subscriber: depressingthe talkelisten butcalled party ,.answers the callby. removing. .his receiver and the. mobilesubscriber.phears, his .voice via the radio receiver 3llfllandthe. lines ;connected with his handset 4ii3.- Conversation oscillator. con pletesthe. output circuit of tube 335' so that now t-he: tone oscillations of approximately 3000 cycles are modulated with the mobile stations l the right-hand winding of transformer 383, conof transmitter' 3fll at contacts 35!.

vton H 5 in handset 433 during talking and releasingthe button while listening.

Upon completion of conversation, the called subscriber replaceahis receiver and releases the connection between the automatic exchange and the. radio control station. When. the mobile sub- 'scriber replacesahishandset 53 the circuitis opened to relay-.363 bythe opening of switch hook springs iilz. Upon restoring, relay 3:35] opens zthezalocking.circuittorsquelch relay. tit atcon- .tacts353, and at contacts-364 completes a kick discharge circuit for the previously charged condenser C2, which lnow discharges through re- ".sistorRe to operatexrelay 349. In operating X .contacts I343,:'re1ay. 34d completes its own obvious locking circuit through contacts 33L. at contacts 13ll,--avcircuit;is completed for relay 4213, which :mayrbe traced frorn ground. atcontacts 3M con- 25111613015392; andcup through the winding of relay mam battery. 1 :At :COIlli&GtS*34i, relay 340 maintainsrelay 325:"operated, thereby keeping trans- "mitteritfll energized, since therestoring of relay 3'63 has opened the-previous energizing circuit At contacts relay 340 complete an obvious circuit for the re1ays35ii and 335. At contacts 344 relay "34B completes a discharge circuit of the previously charged condenser C3 over a path similar to the one traced for condenser C4, and at contacts 346 a circuit is completed for the slow to-operate -relay1336, which at the present does not operate.

Relay "Blu -restores, having no effect on the equipment at the present. In operating, re1ay.335

f-unctionsuas previously described to disconnect .:the:1antennaafrom thereceiver 303 and connect the antennawith the transmitter 3&1. In-operating, relay 350 functions as previously. described,

in which the circuits of tube 335 have been changed for causing the tube to operate as atone In operating contacts 422, relayAZU carrier over-a; circuit which may be traced. from tact 354, resistance R9, conductor 422, conductor .385 'andtothe input transformer in the radio transmitteretiil where the carrier with its-tone modulation-is placed on the air.

However, at the time that the circuits for relays 425, 359/321'161-335 were completed, the discharge circuit for :condenser: C3 was completed. The

discharge of condenser G3 has the same effect on tube 306 as was previously described for condenser C4, so that it will be seen that tube 366- will-cease passing: current while condenser C3 is:discharging.and relay 323 will therefore restore. In restoringat contacts 32!, relay 32!] opens the *energizing'ccircuitof the slow-to-operate relay -330, which'rhas'no effect-since relay 338 had not yetoperated. V

. Duringrthe time that condenser C3 is discharging, tube 'silt does: not pass current and relay 320 is therefore restored, also, the mobilestations -.carrierwismodulated with the tone oscillations .from tube3ll5 andplaced on the air.

predetermined interval of time (slightly less than Afteraa twee-seconds) condenser 03 completely discharges tubetflfi again passes current and relay wfllitmeoperatesi 'The operation of relay 320 completes the'circuitto relay 330 which will operate OVGIHB'H obviouscircuit after the expirationilof its slow-to-operate time and open the locking circuituotrelay. 340;at;contacts 33L Atioontacts 332, relay 330 applies battery potential for shunting down relay 335 over an obvious circuit.

In restoring relay 346 opens the circuitto relay 325 in transmitter 33! at contacts 341, at contacts 34!, the circuit to relay 420 is opened, at contacts 342 the energizing circuit to relays 335 and 35s are opened, at contacts 343, its own looking circuit is opened, at contacts 344, the discharge circuit ior condenser C3 is opened, contacts 345, the charging circuit for condenser C3 is completed and at contacts 346 the energizing circuit for relay 333 is opened.

As relay 335 restores, the antenna is transferred from the transmitter 30! to the receiver 383 and the mobile stations modulated carrier is removed from the air. When relay 325 restores, the transmitter 331 is deenergized. In restoring its operated contacts, relay 35!! changes the circuits of tube 305 for operation as a tone detector. In restoring its operated contacts, relay 429 opens the output circuit from the tone oscillator and connects the transmitter of the handset 403 with the radio transmitter 30 I.

Since the battery shunt applied to the winding of relay 335 by relay 330 will tend to make relay 335 slow-to-release, the actual release of relay 335 becomes effective after relay 340 has restored and at approximately the same time that relays 350 and 42!! restore. Therefore, under average conditions the mobile stations modulated carrier will be placed on the air for approximately two seconds which broadly represents the sum of the discharge time of condenser C3, plus the operating time of relay 330, plus the release time of relay 335. It will be remembered that the duration of this time period may be changed by varying the value of resistance R4, which directly afiects the discharge time of condensers C3 and C4.

The mobile stations carrier modulated with the uninterrupted tone oscillation is received at future calls since tube 336 is passing current and relay 328 is operated, all other relays have restored, tube 335 is conditioned to operate as a tone detector and the antenna is connected with the radio receiver 308.

Incoming call to mobile subscriber The operation of the mobile equipment during the origination and completion of an incoming call from the radio station will now be explained, reference being had with Figs. 3 and 4. It will be assumed that the mobile subscriber ha energized his equipment by the operation of his master switch 498 as previously described in the section entitled Outgoing Call From Mobile Subscriber.

Responsive to the incoming carrier from the fixed, or-radio station, a ground potential is applied to conductor 348, from radio receiver 309, for operating squelch relay 3m. In operating contacts 3l3, squelch relay 3m prepares its own looking circuit. At contacts 3! 4 squelch relay m completes the plate circuit for tube 385 to operate as a tone detector. This circuit may be traced from the positive high voltage source in radio receiver 383, conductor 349, contacts 3l4,

applied to the grid of the tube 335 310, conductor 395, contacts 455, winding of relay 4m, conductor 386, contacts 355 and to the plate of tube 3&5. At contacts (M5, the squelch relays sit at all of the mobile stations opens the original energizing circuits to relays, such as relay 362, to lock out all mobile stations except the called mobile station as will be more fully described hereinafter, and at contacts 3&5 a point in the operating circuit for the relays and magnets of the minor switch 435 is prepared.

The calling subscriber now dials the call number of the desired mobile station to cause the radio station to modulate its carrier with splashes of tone corresponding to the number of impulses in the call number as previously described.

The incoming modulated carrier is received at radio receiver 3% and from there the splashes of tone are applied to the right-hand winding of transformer 383 over a circuit from the output Winding of the transformer in the radio receiver 329, contacts 352 and 353. From the left-hand winding of transformer 383 these splashes are Tube 395 rectifies each incoming splash of tone and completes a circuit upon each splash for operating pulsing relay 4S6. This circuit may be traced from the plate of tube 365, contacts 35l, conductor 335, through the winding of relay 4), contacts 455, conductor 395, contacts 370, 3H5, conductor 3 .9 to high positive battery potential in radio receiver 308.

Upon recepit of the first incoming of the first digit from the radio station, relay 4H3 operates and at contacts 4H completes a circuit to relay 443 and at contacts 4.!2 completes a circuit to motor magnet 43! These circuits may be traced from their respective batteries through the respective windings of relay 448 and motor magnet 433, contacts 4H and M2, contacts 454, 4'33, conductor 398 and contacts 3 l t to ground.

Before continuing with the present explanation, it will be assumed that the callin party is placing a call to the mobile subscriber shown in Figs. 3 and 4, in which the connections on the minor switch bank 405 indicate that the illustrated mobile subscribers call number is the two digit number 47. Relay 4H) will therefore operate and deenergize four times each, upon receipt of the pulses of the first digit dialed. Relay 449 is constructed as being slow-to-release and will remain operated during the pulsin of each digit but will release between digits.

In operating contacts 44!, relay 440 removes a ground potential from the wiper 4GB of the minor switch 495 while stepping. Motor magnet 43%] operates responsive to each operation of relay 4| E) and restores responsive to each release of the relay 4m and advances wiper 43 3 one step upon each release. Ofi-normal springs ON close on the first step of wiper 406 to prepare a circuit for release magnet 435. Since the pulses of the first incoming digit 4 operated relay 4m and motor magnet 433 four times each, it will be seen that the wiper 465 now is resting on the fourth contact of the contact bank.

The pulsing has now ceased for the first digit and relay 440 restores. At contacts 44!, relay 44B completes a circuit for the relay, such as 460, at all mobile stations having the digit 4 for the first digit of their call number. This circuit may be traced from ground at contacts such as 3H5, conductor such as 393, up throu h contacts such as 44!, wiper such as 4518 and its engaged fourth contact, contacts such as 552 and through the winding of relay such as 456 to battery.

zzamaogars .521 IHT'QIDSiHfiOOHfiflQSJfi lyr'elay lfllli also compietes circuit tor;therzzreiease magnetsu5,:aawhichtmay be traced:from'groundiatccontacts :3 I fi c'conductor ;a-, 398,'=s,contacts 44 I ,11 46 I ofienorma1::rcontacts ON randLthroughztherwindingrofrreleasevmagnet lfl atorbattery. x'At "fX'tcontacts 1l65; relay 45 Oizflrst a. completes its f-own locking-circuit, which 'simayi be xtracedi from :iground: at :contactseil fi vaconductor F398,:contacts 413i454e465:;and;througlrtheiwind- :ingjotrelayrlfiIlztorbattery. I At contactsdfiirrelay 460? opens. its previous r'energizin'ga:circuitirand "at contacts-1464; prepares -anl. '=;operating" circuit irfor i relayiflfl.

' .Thezoperation :Tof :release.;:.-magnet 1543 51% restores wiper 406 to normaltin: thewusualzzmannerrand z openswofienormalxr springs ON to ;;open its: :own -circuit.

The: last: digit .f7 r :of thevcallwnumber 4'7f:.is "snow ;;dialed," with:1relay 9110 .andrmotonrzmaanet v 430roperatingarcorrespondingzznumberofzztimes. --.:At the; end of therlastzseri'es ofziincomingrpulses, will :be seenthatwviper zlflfiiisvnow at'rest: on the seyenthtcontactoffithezrcontactsbank. Relay Mlfiyrwhich:zoperatedxrat "the lbeginning rofmzthe pulses of the last digit, now restores and-:aticon- :xtacts fl Iwompletes; aicircuit" iorienergizingrrelay silflathis"circuitamay:ibeiitrace'dz rom iithe ground i."at"?CDnta:CtSl i316, soonductorritSB cntactsivi I, owiperizlnfiandiiitsiengagedzi'seventh:bankvcontact,

2.1101 toibattery.

I aIn":operatingfiX:contacts 2-, relay "4 Ii fir'st w-completesfits own lockingf circuitpand since tm soft-normal springsONahaVemgain beenclosed; at

:to the.mobiler subscriber that z-he -is beingcalle'd won an incoming call. Relay 46n=now resteresand -:r'elease magneti435 operates to restore wiper lflfi v again to 'normalpat whichtime ithe off normal wspnings (9N. open 'r to restore' the release magnet 435.

Responsive "to "the aiidible' sienal "from' buzzer 40 I Ethemnbiie subscriber now removes his handset-403, which eloses the sWitch-hookysprings 4M and'completes a circuit to relay 361]."Ihis cir- -ei1it'may 'betraeed'from ground' at *switch' hook I springs 402; =contacts fl l,conductor 396-tarid f'through 'the windingpf'relay-360 to battery.

It will be understood that at all the mobilestations, the contactsisuch as 3I5 are opened by the squelch" 'rel'ays 'sdch'as 3 I 0" so "that such subscribers cannot operate relayslsuchnas 360 to aor lginate an outgoing call. *iflsin'ce' the relayAFIO ationly-f the .called mobile .station.;.is.goperated to .icloset oontacts 414 to prepare-tan alternatemcircuit I for relay"360,1itwil1;be seen; that: onlyhthel-caHed ;station;can operate relay; 360Woyerlthisalternate .circuitrby'rthe removalpfithei handset,-=all-.other stations iheing. locked out; by l'their inability "to complete.an operatingmircuit for their relays such vWas-i360.

In operating contacts-36 I relay- 36!) vcompletes 'ranobvious .circuitlto 're1ayt325 in fIadiO l trans- .tmitter 30 I at contacts. 363 a-ipoint inzthen talking circuit v.loetvveeni radio rreceiver-r 3D andahandset 5403 "is": completed, atrcontacts 36 SLu-arpOintI-Vin I the charging circuit for thecondensen cza-is prepa-red andtat contacts-361 the discharge circuit for-icon- ,denser C4, .-whichebeeameachargedamzer a; preyicusly traced circuit. is completed. Condenser '22 -:'C4"idischargestto rcause:tube 306:'tor'ceaserpassing urrentzand thereby'releasefrelay 320;;a1lw'ofcwhich as :beenirpreyiouslyidescribed intthea'sectionsaen- 5: titled fiutgoing Call; From; Mobile; Subscriber, andsincethisoperation performs no useful func- L.tion:,at this: time, itiiistthought'that therapresent a description rwiill :siiffice. KIA) contacts I 1368 wrelay 3601 completes ".anzobvious holdingicircuiti fon;the squelch: relay 3 III,- at contacts 369 completes aits wown locking-:circuitpataxcontacts 318 therrhigh voltage :circuit from the. ::radio receiver 300118 ppened to,;prevent charging of A condenser rCZ'gand tat: contacts 3! l5? opens the: audibleesignallingiipir :euit of the-vbuzzer 40].

1" In operating contacts 326,- relayf325 completes the wcircuit l-forw starting dynamotor 315; which provides the-:operating power forradior-transmit- TtenBU Land the handset 493.

32 Conversatiommaynnowvtake DIEICQTiIIIthGQUSHQfl manner, with the mobile :subscriberidepres'sing ihisrtalkr-listen button M5 to speakzand -ireleasing f the button to listen. The operation :ofutheutalklisten". button 4 I 5wc1oses previously traced "circuits :for operating relays-335 and-350. The operation -*-and:. release* of- :re1a f335 takes" "p1aCe r'neach time that thezwtalk listen :button 415 --is 'depressed'nor released and I alternately I connects and disconeneets the :radio' transmitter 30 I and 'receiver" 300 with the t-antenna; as i previously idescrib ed. i'Ifhe eoperationof relay 35flrhaslbeenfullyades cribedrin the section entitled .Outgoing calls-FromtMobile Subscriber, in-which'relay 350 completes a previous-lyxtracedw:charging circuit for the :condenser C25 1 andiithe 1 ,other; functions "as .previously" mentioned.

. AResponsive to the "completion:rof conversation, the callingsubscriber replaces: his; receiver torre- .store:; the 1 exchange equipment aspreViouslyfdescribed, wand whenrthe mobile subscriber'repiaoes handset-4832mm the: switch hookysprings-AM openthe-peircuit to relay 369:then restoresxand at contacts36 I :opens the -circuit to" relay; "325. i-"At contacts-1364, I relay 358 completes arpreviously traced discharge x-circuit for the condenser 402, which upon discharging energizestherrelay 340, and at contacts=366 completes a'previouslyrtraced .circuit for recharging condenser G4.

The sequence of operations followingcthe-renmergizationof *reIayFMOs'has been described inr the isectionsentitled Outgoing Call From MobileSub- .=scriber,ehencepitis:deemed: unnecessaryfrtosrepeat the same in detail and instead willzgbeibriefly outlined. V

r In operating,- as fpreviously described; relayilidfl completes its-ownslockingcircuit, completes circuits for relaysAZfl; :35u-wand-335, maintains srelay 325 operated, completes the discharger-oircuit of condenser: C3 and completes: a circuit "forthe slow-.to-operate relay 33fl.

V imoperatingrrelay r355 completes"thesiplat cir- .tcuitsr ofz'tube 305130 operate asa'tone oscillatonand since: thewantennachas beenswitched' to the-radio transmitter-13B I and relay 42:1 isoperated, the mo- ;bile stations carrier ismodulated;bysthegnninterrupted. tone oscillation from tube3 0 B-andplacedon the air. Inthe-meantime, condenser "IC3i-has startededischarging over: a previouslyvtraced circuit-andicaused tube 896 to 'cease'rtpassingizcurrent! which thereby allows; relay sat-10 restore. The restoring "rote-relay" v329 copensqthe- "circuit sito relay -:330 before that-relay rh'asihadftimetrtoropera-te. Then-mobile 'stationszmoidulated i carrier *Will: remain on :the aircduringthe id-ischargingraof condenser. O3 and format short intervalzthereatter.

iWh'em ;;condenserr. C3:has tcompletededischarging, tube 306 again passes current and relay 320 is reoperated. In operating, relay 323 completes the circuit to relay 330, which will operate after a normal interval of time. Relay 333 opens the circuit to relay 350 and also applies a previously mentioned battery shunt to the relay 335. In restoring, relay 343 opens the circuit to relays 350, 339 and 423, and completes the charging circuit for condenser C3. In restoring, relay 335 removes the mobile stations modulated carrier from the air by disconnecting the antenna from .the transmitter 30! and connecting the antenna with the receiver 33D. Relay 330 now restores with no apparent effect, since the previous energizing circuit of relay 335 has been opened by relay 34d Relays 356 and are likewise restore.

During the time that the mobile stations modulated carrier was on the air, it was received at the radio station for initiating the release of the radio station equipment. The restoration of the mobile station equipment has now been covered, references being had with the aforementioned section entitled outgo ing Call From Mobile Subscriber. All of the mobile station equipment is restored, however, it has not been explained how and when the squelch relay am and the last digit control relay 41B restored. It will be remembered that when relay 351i restored, the locking circuit to the relay 3H! was removed and that relay 3H) will remain operated as long as the mobile station receives the radio stations carrier. Therefore, when relay 335 operated, responsive to the operation of relay 340, the antenna was removed from the receiver 300 and connected with the transmitter 3M so that the mobile station now fails to receive the radio stations carrier. Relay 3E3 thereby restores and opens the circuit to relay ilt at contact 3l6. If, at the end of the transmission of the release pulse when the antenna is returned to the radio receiver ate and the radio station hasnt completely restored to normal, the radio stations carrier is still on the air, relay 3 It may momentarily energize until the radio stations carrier goes off the air.

The mobile station equipment may now be considered at normal and conditioned to handle future calls since tube 396 is passing current and relay 323 is operated, all other relays have restored, tube 335 is conditioned to operate as a tone detector and the antenna is connected with the radio receiver 333.

Before continuing with the present explanation, a short description will follow concerning the operations of the pulse receivers in the other mobile stations when the call number 47 of the called mobile station is dialed.

:When the first digit 4 is dialed, all the pulse receivers in the other mobile stations operate as just described for the called station. All the wipers such as 405 are engaged with their respective fourth contacts of the minor switches contact bank. At this time a previously traced circuit is completed, at the stations whose first digit corresponds with the digit 4, for operating their first digit control relays such as 450. At the remaining of the other stations whose first digit does not correspond with the digit 4, the fourth contact of the contact bank is connected in multiple with the other contacts of the con tact bank that do not correspond with the individual stations call number and a circuit is completed for their lock-out relays such as 453 over circuit which may be traced from ground at contacts such as 3| 6, conductor such as 398, up

24 through contact such as Ml, wiper suchas 436 and its engaged fourth contact, the multipled connection and through the winding of relay 450 to battery. In operating, all relays such as 450 lock operated to the ground at contacts such as 313. by way of their X contacts such as 453. At X contacts such as 254, the relays such as 45!! remove the operating ground for the motor magnets and relays of the pulse receivers,

at contacts such as 451 a previously traced circuit for the release magnet such as 435 is completed, at contacts such as 452 a circuit is completed for lighting all busy lamps such as L8 and at contacts such as 555 the pulsing circuits to relays such as 4 I 3 are opened.

Thus it will be seen that after the first digit has been received at the mobile stations, all stations whose first digit of their call number does not correspond with the digit dialed will be locked out and their'pulse receivers will be inoperative for the remainder of the dialing and during the time the connection is maintained. Only the pulse receivers of the stations whose first digit corresponds with the first digit dialed remain operative.

The last digit 7 is now dialed and at only the called station, whose contact bank is wired accordingly, will a previously traced circuit be completed to the last digit. control relay All] for signalling the mobile subscriber. At the remainder of the mobile stations, since the seventh contacts of their contact banks are connected in multiple with the other contacts-not corresponding to their individual call number, a previously traced circuit is completed to their lock-out relays such as 458. The operation of relays such as 450 maintain the remaining mobile stations, whose first digit corresponds to the number 4 of the first digit dialed but whose second digits do not correspond to the number 7 of the last digit dialed, locked out during the time the connection lasts.

It will be remembered that the digit 1 is not used as either a first digitor second digit of-any of the mobile stations call numbers, since a false pulse may sometimes occur due to a burst of static or interference and cause the pulse receivor to step erroneously. Therefore the first contact of each of the contact banks has been connected through the off-normal springs ON to the release magnet 435. Thus, if a false pulse occurs, the minor switch will step one step, the off-normal springs ON will close and a circuit is completed to the release magnet 435 for restoring the switch to normal.

Minorszoitch using three-digit call numbers The operation of the minor switch shown in Figure 5 will now be explained. Since relay i50' controls circuits similar to that of relay 450 (Fig. 4;), and relay 430 controls circuits similar to that of relay ill], it is believed unnecessary to describe in detail the circuits controlled by these relays and only'the circuits for operating these relays will be described. All the reference num' bers have been given primes to correspond in part to the same number used to identify similar parts shown in the minor switch of Figure 4.

By removing minor switch 4&5 from Figure 4 and inserting minor switch $05 (Figure 5) into its place, it will be seen that relay 555 will also control contacts 452 and 455, and relay 430 will control contacts M4 and M5.

Assuming that the contact bank of minor switch 405' is wired as shown, the call number of this particular mobile station will be the three digit sam'emanner' as described iorithe'first digit, with.

wiper- A 06 finally :stopping ion the seventh con-- tact :otxzthescontact bankyat thevend ofthe pills-v ingcycle: At=ithisztimeprelays4H3 and MB" and magnet 43M willwhave restored and s the ground in potential issreconnected towiper liiii, thus com-1- pleting acircuitfor relay 410". This circuitmay beLtIaCEd from -thLgr0undi0l1 swiper liiii and itsv engagedseventh contact; contacts 46 3 413, and.

(Figure 3) responsive to thehoperation of relay. through. thc-lw-indingiof relay-finite: battery. In

Before continuing with the present'descripr tion, it will be assumed that minor: switch iii'ilfi has v. been substituted in place of minor. switch 405; that anincoming call to the mobile stat-v tion,; corresponding .with..the call number @7853 has (been initiated: and that the mobile equipe ment has operated asndescribed inrthe previously mentioned section up to the point at which. the 1 first digit is received:

Assuming now that the firstldigit dialed is the number "4 of:.the callnumber-:478. Four rectified pulses are transmitted .by vthe i tonedei tector 'of tubeBiJfifor completing a'circuit to relay :diii' which operates upon receiptof each' pulse and restores between pulses. In ope-rating; relayed I it? completes: a circuit; to: the relay Mit at i'contactsqzd H," and ziticontacts M2; completes a circuit to motor: magnet 438'. Sihoearelay 440?:ihasvzbeenzlconstructed as abeing slows-to-zree 3O lease; it wiitoperate ascsoonas :contactsxti i i i are n closedandc'remain operated during pulsing 0f':1

layrlfig" and release betweenaweachzldialed"digit; Motor magneti tfillf operates .as soon as contacts to 4125i close andxreleases. as soon as contacts: 4121 open; .Ihe operatingkcircuits for relay: M6 and in motor magnet we "maybe tracedirom' ground i at? contacts 3H5, c0ntactsw4B'2f, 454", 4H andmMil' and through'the windings of relay ldii" andumagnet ESiltto battery,respectively. This w andt ilfi whichxrespectively preparesa circuit ifors interaction between motor magnet itt and' re lay it til; continuesnuntil i each series -of l pulses end-:2,

Upon each: restoration of-mot0r magnet 430";

willarbcseenvlthat at the end of the-first series of pulsesgwipeniilfif; willJrest onthe fourth contaet tofithe contact bank. Responsive to -wiper 496i: engaging. with" the fourth contact a of its a relay .459; The first operationof relay Mil had 1 removed;groundifrom wiper. 365": by Opening con-' 1 tflCtSuiQ", however at the end of the first series:

of .rpulsesr relay 343; restoredand reconnected:

themgroundxzpotentialwtoz wiper iilfii by closing c5 contactsMH; The circuitfor relay 13601.. may betraced. from-i'ground. at; contacts I 3 l6 contacts 44 U5, wiper 2.4066- and its :associated iourth contact'gscontactsydfifi zandwthroughmthe winding of 1 relayAfiOf-to battery:

In toperatingi XI contacts iflflf, relay 466' completesxits ownlocking circuit over an obvious i path before opening its original energizing in: on! OUiULaEJCOIItEAQtS 4821'," atrcontacts 464') prepares:

operatingMXt contacts 4'l4 ,relayrdifi* come pletesits own lockingicircuit over a similar path: as that for relay 460' before opening its energizingxcircuit:atacontactsufly, and at contacts 5 il? prepares a circuiti for relay .480".

Sincerelayiififl is stilLoperated and relay 440 has restored-due vtozthe 'endiof the "second 'series of'i' pulses, a'circuit is again; completed for re-* lease magnet i130, whichxrestoreswiper 36:6? to:.- i norrnallfor iax'secondritimes The last digite 8 of the call- .number; isnow dialedandvrelays Mus-and 440 and magnetndiw again. a operate x as" previously' described; with wiper 1. 4081:? engaging; :the @eighth contact of lithe": contactlbank? at tthez'end fiofmthezlast seriesvx-of p pulses At this 1 time;v ancircuit is l completedcfor r;

relay 48iiflfwhichtmay bectracedfrom ground on WiperAHS' andnitsengaged eighth contact; coni tactsA'lZf-and through thawinding of relay stil ,to battery; In :opcrating (XVcontacts 58i, re-

'layw 48 t "completes its own "locking circuit to: the

grounduatt contactst3 16%. At contacts 482:? re-w iay'48E3 opens the :lockingacircuits of relay sec?- and ild. and theyzrestore: Atcontacts 283'; re'-=- layu iiiii prepares 'a'vcircuit for the release magnet 635 so; thatewheniirelayq 4413f restores"; the:- circuit forxenergizingrmagnet 7435- 1 is then completed for returning wiper 40% to normal. n Then operation of relayABfl also "closes contacts M4 operatingzrelay 360 "(Figure 4) and for signalling the mobileisubscriberrof sanincomingrcall in the-same manneras described for Figure 4. i

A general :lcallifeaturet is also i provided in this wiper al lfiiii is advanced one step and-thus it --.-switch, in whichallcitheimobilesubscribers maybe signalled;esimultaneously by the central toffice in response to the dialing of a :single: digit 0} Relay 48ilf'i-isloperated in the same manner 1 as relay-4 "tB- (Figure.14) whichhas been describedxt contactbankjaVcircuitis completed for operating 50min the previous.sectiornentitled Incoming Call To '-Mobile Subscriben": and which 'operates toe signal all the: subscribers. by closure of contacts It wil1 be tunderstood that ifiacall. number" is a dialedpinzwhich .onezofi thewdigits does not: corre spend with the illustrated:subscribers: call -num-. berg the l relay-45E iwill'vioperate :responsiveto receipt of the different. tdigitilto :halt. any subse-s quent l operation? of. the uminorrswitch and locks-1i (rout the mobile subscribereunti-ll the x'call. is :termie.

nated or abandoned.

Having describedsthe;invention; what is coni-1- sidered inewand: desiredttdxhave protected by Letters Patent will be pointed outsinuthe-apw a circuitfor 1613137479 andiat contacts 451: comtotiwpendedclaims pletesia circuit to the release magnet 35k Since ofienormalssprings ON were closed responsive: 1 to zlwiper. 14 U 6 stepping ofliznormal, the circuit for I magnet 455 may be tracedirom ground at con- ONrand through: the winding of magnet 435' to batteryr Release magnet 4351 now restores wiper 460; to :normal. r

The second-idigitxff'z?sis ;:now L dialed andtrelay. x

What is claimed is':

1. In a mobile radioe'telephone system; a: radio controlzstationg': mobile stations, means. respon- 1 siveto theiinitiationliof ascall. bya calling one of tacts Slfifycontactsfidlfl cal; off-normal springs tsaid= mobilestationshfior; transmitting :a mobile radio frequency carrier onthe air, means Said it controls station; L operatede responsive .to- "the zzreceipt otcsaid transmittedx mobile :carrier" fort transmitting ",a ncontrolv lstatiorrsradio frequency 4 l Mrmagnetuflfl and LreIayvMO-H operate i in: the 1575 ;f.-carrier;..on1;the dair locking agm'eans 1 operated 'zin transmitting means for maintaining said control station transmitting means in operated condition to maintain said control station carrier on the air, means responsive to the severance of said call by the calling mobile station for transmitting a modulated mobile carrier release pulse of predetermined duration, and means in said control station operated only in response to the receipt of said modulated mobile carrier pulse of said predetermined duration for releasing said locking means to remove said control station carrier from the air.

2. In a mobile radio telephone system, a radio control station, mobile stations, means responsive to the initiation of call by a calling one of said mobile stations for transmitting a mobile radio frequency carrier on the air, means in said control station operated responsive to the receipt of said transmitted mobile carrier for transmitting a control station radio frequency carrier on the air, locking means operated in response to the operation or" said control station transmitting means for maintaining said control station transmitting means in operated condition to maintain said control station carrier on the air, impulse transmitting means in said calling mobile station for transmitting modulated pulses of said mobile carrier to extend a desired connection, means responsive to the severance of said call by the calling mobile station for transmitting a modulated mobile carrier release pulse of predetermined duration, and means in said control station operated only in response to the receipt of said modulated mobile carrier pulse of said predetermined duration for releasing said looking means to remove said control station carrier from the air.

3. In a mobile radio telephone system, a radio control station, mobile stations, means responsive to the initiation of a call by a calling one of said mobile stations for transmitting a mobile radio frequency carrier on the air, a squelch relay in said control station operated in response to the receipt of said transmitted mobile carrier, means in said control station responsive to the operation of said relay for transmitting a control station radio frequency carrier on the air, locking means operated in response to the operation of said relay for locking said relay in operated condition to maintain said control station carrier transmitting means in operation, means responsive to the severance of said call by the calling mobile station for transmitting a modulated mobile carrier release pulse of predetermined duration, means including a slow-tooperate relay in said control station operated only in response to the receipt of said modulated mobile carrier release pulse of said predetermined duration, and means controlled by the operation of said slow-to-operate relay for restoring said locking means to thereby restore said squelch relay and remove said control station carrier from the air.

4. In a mobile radio telephone system, a radio control station connected to an automatic telephone exchange having a plurality of fixed automatic subscriber stations connected thereto, mobile stations, means in said control station responsive to the initiation of a call by one of said fixed stations to a called one of said mobile stations for seizing said control station, a radio transmitter in said control station operative in response to said seizure for placing a control station radio frequency carrier on the air, means at said control station responsive to subsequent dial pulses received from said calling fixed station for modulating said control station carrier in accordance with said received pulses, means in said called mobile station operative in response to said control station modulated carrier pulses for selecting and signalling said called mobile station, means including a handset and a radio transmitter at said called mobile station for completing said connection over the air between said calling fixed station and said called mobile station, maintaining means in said control station operative for maintaining said control station carrier on the air during conversation and after said calling station disconnects from said connection, means at said called mobile station operative in response to the called subscriber replacing said handset for operating said called mobile radio transmitter to place a mobile radio frequency carrier on the air and for modulating said mobile carrier to transmit a modulated release pulse, and means in said control station operative only in response to said modulated release pulse for restoring said maintaining means to remove said control station carrier from the air. a

5. A telephone system such as claimed in claim 4:, including time delay equipment at said called mobile station operative responsive to the replacing of said handset by said called mobile station after a predetermined lapse of time for halting the transmission of said modulated release pulse and the transmission of said mobile carrier to thereby fully release said connection.

6. A telephone system such as claimed in claim 4, wherein said last means includes a detecting means operated responsive to receipt of said modulated release pulse for rectifying said pulse, and a relay operated responsive to said rectified pulse for initiating the restoration of said maintaining means.

'7. In a telephone system for extending calls over a radio link between a first group of connected subscriber stations and a second group of isolated subscriber stations in response to dial pulses initiated by the calling subscriber; each of said isolated stations including a handset, a radio transmitter, an electronic discharge 7 device and an antenna normally disconnected from said transmitter; means operated responsive to the removal of said handset by one of said isolated subscribers when calling for energizing said transmitter at the calling station, for connecting said transmitter with its antenna to place a radio frequency carrier on the air for seizing said control station; a radio control station, a dial at said calling station initially rotated by the calling subscriber subsequent to the removal of said handset, a first relay operated responsive to said initial rotation of said dial for preparing said electronic discharge device to operate as a toneioscillator, a second relay intermittently operated when said dial returns to normal for causing said electronic discharge device to transmit intermittent pulses of tone to modulate said carrier transmitted to said control station for extending said call, and means operated responsive to the restoration of said first means by said calling subscriber replacing said handset for reoperating said first relay to again prepare said electronic discharge device to operate as a tone oscillator and to operate said second relay for a predetermined interval of time for allowing said electronic discharge deviceto transmit a steady pulse of tone,rcorre- 29s sponding to said interval f 'jtimegxto modulate saidlcarrier .for. initiating the. release of said control station.

8. A telephone system such as claimed in claim 7, including an electronic timing arrangement,

a circuit controlled responsive to the operation of-zsaid last means for initiating acurrent flow" inrsaid-timing arrangement, and-means1,icontrolled by the operation of said=timing arrangement after a predetermined interval of time;co1

responding to said current fiow reaching a predetermined value, for restoring-said lastzmeansx to subsequently restore said first, and second relays and thereby halt the transmission of said steadysmodulated tone pulse;

9. A telephone system: such: as claimed in claim 7, v,wherein said last meansincludesga relay, and a condenser for energizing said relay, a circuit controlled by said first zneansfor charging said condenser with a high potential, and another circuit including said charged condenser, controlled by said first means, for initiating the operation of said relay.

10. In a telephone system for extending calls over a radio link between a first group of connected subscriber stations and a second group of isolated subscriber stations in response to dial pulses initiated by the calling subscriber; a radio control station, a handset at each said isolated station having a normal position, a radio transmitter at each said isolated station, means operated by a calling one of said isolated stations responsive to the removal of said handset from normal for energizing said transmitter and placing said transmitters radio frequency carrier on the air to seize said control station, an electronic timing device initially energized responsive to said first means operation to operate after a predetermined time interval for removing said transmitters carrier from the air, and means operated responsive to the restoration of said first means, when said handset is replaced to normal, for replacing said transmitters carrier on the air and for initiating and transmitting a timed release pulse to modulate said carrier transmitted to said seized control station for initiating release purposes thereat, said operation of said last means also initiating the reenergization of said timing device to reoperate after a predetermined time interval for restoring said last means to normal and thereby halt the transmission of said modulated release pulse and said carrier.

11. In a telephone system for extending calls over a radio link between a first group of connected subscriber stations and a sec-ond group of isolated subscriber stations in response to dial pulses initiated by the calling subscriber; a radio control station, means in said control station operated responsive to the initiation of a call by a calling one of said first group of subscribers for seizing said control station, a two-digit call number individual to each of said second group of isolated subscribers, means in said control station operated responsive to the dialing of a desired one of said two-digit call numbers by said calling subscriber for transmitting pulses corresponding to said dialed two-digits to each of said second group of isolated subscribers, means at each of said isolated subscriber stations for receiving said transmitted pulses, each saidisolated subscriber station including an electronic discharge device for rectifying said received pulses, a pulsing relay operated responsive to receipt of said rectified pulses and a pulse receiver operall other-isolated subscriber; stations that,;sa1

radio control-station is buss/sand means ats called stationpperated responsive. to the sever, ance; of; said: call; by said :(CZLHQCL subscriber for;- transmitting a release pulse to; said; control xStfimtionrto, initiate, therelease of said control station 12.,,A telephone systemzgsuch as, 1 claimed 1 claim 11,,including.aminoryswitchin eachots pulse receivers having a single 1contact'bank an wiper, said wiper: shaving access 1- to ;sa id;,contact-; bank;- amspecial call number comprised of one digit having a predetermined value, a certain contact on each of said contact banks corresponding to said special call number, and means operated at each of said isolated stations responsive to said wipers engaging said certain contacts, in response to said minor switch being operated upon receipt of pulses corresponding to said special call number, for completing a circuit to signal all of said isolated subscribers simultaneously.

13. In a radio telephone system, a radio control station having a radio receiver and radio transmitter, a first relay in said station connected to said receiver and operated in response to the receipt of an incoming radio frequency carrier received by said receiver, means controlled by the operation of said first relay for activating said transmitter to transmit an outgoing radio frequency carrier over the air, a second relay, a first circuit for operating said second relay closed responsive to the operation of said first relay, a second circuit closed by the operation of said second relay for maintaining said first relay operated after termination of said incoming carrier, means including a third relay in said control station operated in response to the receipt of a modulated release pulse of said incoming carrier, normally closed contacts included in said first circuit operated by the operation of said third relay for opening said first circuit to restore said second relay, the restoration of said second relay opening said second circuit to restore said first relay after termination of said modulated carrier pulse, and the restoration of said first relay controlling said transmitting means to remove said outgoing carrier from the air.

14. A radio telephone system such as claimed in claim 13, wherein said last means includes an electronic tone detector operated responsive to the receipt of said modulated release pulse for detecting and rectifying said pulse, and a pulsing relay operated by said release pulse for operating said third relay. 15. A radio telephone system such as claimed in claim 13, wherein said third relay comprises a slow-to-operate relay and wherein said last means includes a pulsing relay controlled by modulated switch controlling impulses of said incoming carrier, and a circuit controlled by said pulsing relay normally ineffective to operate said third relay in response to said switch controlling impulses and effective only in response to said modulated release pulse of a predetermined duration.

16. In a radio telephone system, a mobile sta- 75 tion having a radio transmitter, a condenser in 

